1. Field of the Invention
The invention relates in general to illuminators for illuminating a field of view, and in particular to a device for intraocular application of a slit-shaped beam to ocular structures for purposes of diagnosis and treatment of ophthalmic conditions.
2. Related Art
The use of an externally-applied slit-shaped light beam has been known in office and surgical settings for illuminating ocular structures, such as the cornea and lens surfaces and intraocular fluids. These structures, which are nearly-transparent, are difficult to distinguish using conventional illumination due to the small amount of light scatter which they produce when diffusely lit. The use of a slit-shaped beam allows selective, directed, and intense illumination of nearly-transparent tissues such that even a relatively small amount of scatter by such tissues allows them to be distinguished and otherwise observed or targeted for surgical modification or removal. The slit-illumination also provides a sense of depth, thickness, and three-dimensions to these transparent structures, especially when applied obliquely.
Fiber optic intraocular light sources are known. Such sources have been incorporated into intraocular scissors and forceps for illuminating the proximity of the distal end of such instruments. However, such devices have not provided the advantages of slit-beam illumination, e.g., selective, directed, and intense illumination of target tissues with high contrast.
U.S. Pat. No. 4,138,191 to Peyman et al. discloses a stereo viewing operating microscope for use in optical microsurgery. The microscope is provided with an external slit-shaped beam source for illumination. The slit-shaped beam source is movable, independent of the viewing optics, on an arcuate track.
U.S. Pat. No. 4,565,197 to Daly discloses an aiming/illumination system for use in conjunction with an invisible beam laser for microsurgery procedures. The invisible beam and an aiming (visible) beam are applied along a common axis which is displaced with respect to that of a slit lamp beam and also is displaced with respect to a line of sight of viewing optics. All three axes converge at a common focus point, providing selective illumination/targeting of an area of interest. The system disclosed is non-invasive, with all three light sources being applied externally to the eye.
The aforementioned prior art devices suffer from the disadvantage that ocular structures (i.e., the cornea) which intervene between the light source and the target tissues cause scattering of the illumination light, thereby increasing glare and reducing contrast of the target tissues with respect to such intervening structures and lowering the intensity and quality of the illumination light reaching the target tissues.